Rotary steerable systems (RSS) were first introduced as push-the-bit systems in the late 1990s and were drilling in manual mode sending downlinks by mud pulses downhole. The point-the-bit RSS was introduced in 2003. The first automated mode, known as inclination hold, was introduced in 2003. This was followed by vertical mode in 2004 and by hold inclination and azimuth mode in 2008. The last well profile type, the curve section, was not automated until 2020 when curve control was implemented for push-the-bit RSS. Implementing curve control for push-the-bit RSS has reduced the frequency of downlinks sent from surface and has improved the rate of penetration, thereby supporting a sustainable digital solution for directional drilling and drilling engineering. Curve control for point-the-bit RSS was introduced to the field in mid-2022 and has opened new applications for downhole automation. Point-the-bit RSS has a different steering mechanism (fixed bend) and it has the sensor offset farther from the bit, which creates challenges for implementation of trajectory automation.

In our work, we analysed several case studies and examined new application opportunities for autonomy for trajectory automation based on the field results. Until mid-2022 directional drillers sent manual downlinks to point-the-bit RSS from the surface to follow a planned trajectory and hit the target. These downlinks sent a steering ratio to achieve desired dogleg severity (DLS) and a desired toolface to turn the well if needed. By introducing downhole automation, the Directional Driller is able to send curvature commands, and the tool determines steering ratio to achieve planned DLS by applying a closed-loop algorithm to drill the trajectory. The closed-loop system minimizes the influences of variations of weight on bit, RPM, and formation characteristics on trajectory response.

Point-the-bit RSS have shown the ability to drill different curve profiles in curve control mode from 2D build to 3D build or drop. Some of the trajectories included a tangent section that were executed with DLS demand of zero. The case studies demonstrate that curve control mode has drilled entire hole sections while reducing the frequency of downlinks, increasing the rate of penetration, and increasing consistency.

Our work examined the next level of downhole automated directional trajectory control for point-the-bit RSS that is currently handled and controlled by the directional drillers (e.g., geometric and geological steering). The curve control mode minimizes the interactions with the surface and allows the driller/surface system to optimize the drilling parameters. The algorithm also minimizes the influences of variations of weight on bit, RPM, and formation characteristics on the trajectory response.

You can access this article if you purchase or spend a download.